Technical Field
The invention relates to molded plastic parts used for vehicle lamp reflectors.
Background Art
Bulk molding compound (BMC) is a widely used material to make modern automotive light devices. BMC is a combination of resin, glass fiber, and filler materials mixed into a compound that can be injection molded into complex parabolic shaped parts that are coated with metal to form parabolic reflectors for the light device. Although the glass fibers and fillers improve strength reduce overall cost of the BMC based reflectors, these materials can cause the BMC molded part to have a rough irregular surface. Direct metallizing of such surface generally results in a poor quality reflector that cannot provide the optical properties necessary for many vehicle lighting functions. In particular, the directly applied metallization layer has the same surface irregulaties as the BMC part, and hazing often occurs on the metal possibly due to outgassing from the BMC resin.
To address these problems, an acrylic base coat is applied to the surface of the BMC part where the reflector is to be formed. This base coat evens the rough surface of the BMC part to provide the smooth base needed for a reflector, and prevents hazing that occurs on direct metallized BMC parts. However, the base coat must be applied by a complex spray coating and curing process that requires large capital and floor space investment. Thus, there have been efforts to provide a BMC reflector that meets optical requirements for vehicle lighting without the use of a base coating. For example, U.S. Pat. No. 5,865,530 discloses a BMC formulation and molding process that improves surface smoothness such that metallization may be directly applied to the BMC part. Nevertheless, the resulting reflectors do not provide photometric properties suitable for many vehicle lighting applications, and often have hazing which is aesthetically undesirable for clear lens vehicle light devices. Thus, the processes disclosed in U.S. Pat. No. 5,865,530 have not been widely adopted by the vehicle lighting industry, and base coating is generally accepted as a necessary process for producing high quality vehicle light reflectors.
The “background” description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description which may not otherwise qualify as conventional art at the time of filing, are neither expressly nor impliedly admitted as conventional art against the present disclosure.